1. Field of the Invention
The present invention relates to torque sensing technology and more particularly, to a non-contact type torque and angle of rotation sensing device for use in any torque transmission device to measure the torque on the torque transmission device and the angle of rotation of the torque transmission device in a non-contact manner. The invention relates also to a torque and angle of rotation measurement method using the non-contact type torque and angle of rotation sensing device.
2. Description of the Related Art
In line with the worldwide trend of environmental protection and energy saving, the utilization rate and popularity of electric bicycles keeps growing. Except the mechanisms used in a regular bicycle, an electric bicycle further comprises a battery, a drive motor, a controller, a torque sensor and other electronic control components. When riding an electric bicycle, the torque sensor of the electric bicycle will measure the rider's pedaling force and provide a corresponding signal to the controller, enabling the controller to control the drive motor output power to the bicycle subject to the detected torque. The greater the rider's pedaling force is, the higher the output power of the drive motor will be. Thus, manpower needed in order to save riding. Thus, an auxiliary power can be automatically provided to drive the electric bicycle, enabling the rider to ride the electric bicycle with less effort.
Many different kinds of torque sensing devices have been created for electric bicycle applications. For example, a strain gauge may be installed in a pedal crank of an electronic bicycle to measure the deflection of the pedal crank, thereby providing an electrical signal indicative of the torque. Alternatively, a strain gauge can be installed in a transmission component of an electronic bicycle to detect tiny deflection of the transmission component during torque transmission, thereby estimating the torque.
U.S. Pat. No. 6,644,135 discloses a torque sensor, entitled “Torque sensor for a bicycle bottom bracket assembly”, which comprises an axle supporting member for supporting the axle for rotation around a support axis, and four pressure sensors mounted on the axle supporting member. During rotation of the bottom bracket axle, the torque is directly transmitted to the axle supporting member, causing each pressure sensor to generate a corresponding pressure. The generated pressure is then converted into torque.
The aforesaid conventional torque sensing devices commonly use a strain gage or pressure sensor in direct contact with the mounting location to convert the deflection rate of the structure of the mounting location into torque. However, the structural deflection state of the mounting location varies with the composition of the material of the structure of the mounting location and its manufacturing process, causing the strain gage unable to accurately measure the actual torque value. Furthermore, conventional torque sensing devices commonly have a complicated structure, or will be directly exposed to the outside open air after installation. Therefore, conventional torque sensing devices cannot take into account the installation requirements of simplicity and sense of beauty.